Question: 5 glue sticks cost $6.70. Which equation would help determine the cost of 12 glue sticks?
Explanation: There are several equations that could help determine the cost, each with a slightly different approach. We can write the fact that 5 glue sticks cost $6.70 as a proportion: $\dfrac{5}{\$6.70}$ Let $x$ represent the unknown cost of 12 glue sticks. Since 12 glue sticks cost $x$ , we have the following proportion: $\dfrac{12}{x}$ The cost changes along with the number of glue sticks purchased, and so the two proportions are equivalent. $\dfrac{5}{\$6.70} = \dfrac{12}{x}$